Both morphological and biochemical investigations of MED myopathy, a model hereditary and delayed disease of the motor unit, will be continued. In some ways, this murine disease resembles congenital motor neuron disease syndromes in man. Previous work in our laboratory has demonstrated that MED muscle brei explants regenrate and grow in normal litter mates ultimately resulting in a functional muscle. In the reverse experiment, regeneration of normal muscle in MED recipients is retarded. Biochemical investigations have yielded data indicating a defect of protein synthesis in MED skeletal muscle. Our current hypothesis is that the effects of the MED gene are expressed by an alteration in the balance of protein synthesis, particularly in muscle which possibly is mediated by a neural, "trophic" factor. The proposed work will continue both morphologic and biochemical lines of investigation to better characterize the pathogenesis of this model myopathy. BIBLIOGRAPHIC REFERENCES: Zacks, S.I. and Sheff, M.F.: Reversal of a hereditary myopathic lesion (MED) by transplantation of affected muscle. J. Neuropath. & Exp. Neurol. 34:107, 1975 (abstract).